1. Field of the Invention
The present invention relates to a detection device for detecting an obstacle within a target region by emitting a laser beam to the target region, which is suitable, for example, to be mounted on a moving object such as a vehicle or an airplane.
2. Description of the Related Art
In recent years, vehicle-to-vehicle distance detectors and distance detectors using laser beams have been employed in various devices. A vehicle-to-vehicle distance detector, for example, detects the presence or absence of an obstacle and measures a distance to the obstacle by detecting reflected beams that are obtained when laser beams are radiated from a front portion of a vehicle.
In this case, the laser beams are caused to longitudinally and laterally scan a target region preset in a front space. A time difference between timing for radiating the laser beams and timing for receiving the reflected beams is measured at each scan position, and a distance to an obstacle located in front of each scan position is calculated from a result of the measurement.
JP 11-325885 A describes a technique for detecting a deviation between a driving direction and a laser beam irradiation direction using an acceleration sensor to align the laser beam irradiation direction with the driving direction.
When the driving direction turns to, for example, the right or the left, it is particularly necessary for the detection device to detect as early as possible an obstacle located in the direction to which the driving direction is turning, in order to achieve adequate control in subsequent driving. During high-speed driving, it is necessary to detect an obstacle located at a long distance ahead in the driving direction early enough so that the detection information can be reflected on driving control. When an obstacle is detected ahead in the driving direction of the vehicle, it is particularly necessary to monitor movement of the obstacle and a state thereof in great detail.
JP 11-325885 A describes a technique for aligning the laser beam irradiation direction with the driving direction. However, JP 11-325885 A does not describe how to control a laser beam scan state to be adapted to a high-speed driving mode and an obstacle detection mode. JP 11-325885 A includes no more description than that the laser beam irradiation direction is merely adjusted so as to suppress the deviation between the laser beam irradiation direction and the driving direction when the driving direction changes.